The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Control devices for air conditioning or refrigeration units are known in the most varied embodiments from the prior art. Simpler air conditioning or refrigeration units are equipped with control devices based on mechanical principles, whereas higher quality air conditioning or refrigeration units frequently have electronic control devices of the aforesaid type in which a microprocessor controls all the control or regulation procedures. In addition to the desired room or cooling temperature, where required, the switching on and off or the speed of a fan as well as the triggering and ending of a defrosting procedure and possibly also even further procedures can be controlled by the microprocessor.
Air conditioning and refrigeration units furthermore generally have a coolant circuit in which a compressor, a liquefier, an expansion valve and an evaporator are arranged sequentially in the direction of flow. For a reliable and efficient operation of the coolant circuit, it must be ensured by a suitable control of the expansion valve that the coolant reaching the evaporator is evaporated as completely as possible in the evaporator. To realize this goal as best as possible, electronically controlled expansion valves are increasingly being used which have some advantages with respect to the precision of the control to be achieved over the otherwise customary thermal expansion valves.
Electronically controlled expansion valves are, however, comparatively expensive and furthermore, unlike thermal expansion valves, require their own electronic overheating control for the processing of sensor signals coming from the coolant circuit. In addition to the additional cost effort for an electronically controlled expansion valve, there is therefore additional effort to be made cost with respect to the electronic overheating control and with respect to the sensor system separately required for the overheating control.